The Role of Mycorrhizal Fungi in the Inter and Intraspecific Competition of Nicotiana glauca and Vachellia gerrardii

TL;DR

This study shows that mycorrhizal fungi help invasive Nicotiana glauca grow better than native Vachellia gerrardii, giving it a competitive edge.

Contribution

The study reveals that AMF symbiosis enhances the competitive advantage of invasive Nicotiana glauca over native Vachellia gerrardii.

Findings

AMF symbiosis significantly improved growth parameters of both species, especially Nicotiana glauca.

Nicotiana glauca showed higher root indices and relative yield compared to Vachellia gerrardii under AMF treatment.

Photosynthesis increased in AMF-treated plants, particularly in Nicotiana glauca.

Abstract

A competition experiment between Vachellia gerrardii and invasive Nicotiana glauca Graham was conducted to assess the impact of Arbuscular Mycorrhizal Fungi (AMF) symbiosis on the inter and intraspecific competition between the two species. Seedlings were established under mono and mixed plantations with different species proportions (3:1, 2:2, 1:3) and plant densities (1, 2, 3, and 4 plants/pot) for mixed and mono planting respectively, with and without AMF. The vegetative growth parameters (height, leaf area and number, total dry weight/plant, relative yield, relative yield total), roots characteristics (length, surface area, volume, tips number), competitive interaction (aggressivity), and physiological traits (chlorophyll a, chlorophyll b, photosynthesis, stomatal conductance) were measured to evaluate plant responses to AMF symbiosis and competition. The results revealed that AMF symbiosis significantly enhanced the vegetative parameters (leaf area, height, and total dry weight) in both species under mono and mixed plantations compared to plants without AMF. Under AMF treatment, in the interspecific competition, most vegetative and root parameters of N. glauca were higher than V. gerrardii. At inoculant and species proportions, the relative yield of N. glauca exceeded that for V. gerrardii; however, N. glauca was more aggressive towards V. gerrardii. N. glauca root indices were higher than V. gerrardii under inter and intraspecific competition. Simultaneously, for both species, in monoculture plantations, most parameters decreased as plant density increased, wherein the decrease was higher for plants grown without AMF. Photosynthesis increased in AMF treatment, particularly for N. glauca. In conclusion, AMF promoted the growth of invasive N. glauca more than native V. gerrardii, particularly in terms of the root system. Our results provide a critical perspective that the AMF has the potential to contribute and facilitate the invasion of N. glauca, as well as support it with a competitive advantage over V. gerrardii, thus highlighting its potential role in shaping plant–plant interaction in invaded habitats.

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